A firing mechanism for installation or a muzzle-loading firearm is disclosed. The firing mechanism has a drum means which is attached to the muzzle-loading firearm at a point adjacent its breech. A cap holder fits to the firing mechanism and holds a firing pin. The firing pin fits within a cylinder defined by a portion of the cap holder and drum means. The cylinder defines a closed chamber so that there is no blow back of gases and so that the ignition cap is closed from the exterior of the firearm.